To take this a step futher. Rental property is only exempt as business purpose if its for credit extended to acquire, improve, or maintain rental property (regardless of the number of housing units) that is not owner-occupied is deemed to be for business purposes.
So...if you were refinancing credit originally for the above purposes, it would be BP.
This does not sound like it was purchase money, since it's a HELOC and it's very difficult to determine what the HELOC money was used for, for instance, improvements or maintenance.
If you can't determine these things, then chances are you will keep this as a personal purpose loan.
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My opinion only. Not legal advice.
Say you'll haunt me - Stone Sour